Dawn,
 
Humans can get exactly that smell on their breath, typically caused by
being in a state called Ketoacidosis.  This happens when someone is having
to burn fat/tissue for energy.  Possible causes in the human are diabetes
out of control, starvation, and very low carbohydrate diets.
 
If this is something your vet doesn't already know about, Tazy may need to
go in.  Prednisone does raise blood glucose, and could be a problem in a
diabetic.  Has Tazy ever had pancreatic surgery?  Maybe prednisone plus a
debulked pancreas would have an additive effect.  I'd want a glucose level
to start.
 
I hope Tazy gets better quick!
 
cb
[Posted in FML issue 3345]